The invention disclosed relates to a control device for monitoring the quality of cigarettes fed into a packaging machine.
In conventional packaging machines, cigarettes are generally fed to the wrapping line from a chute provided internally with baffles by which adjacent channels are created, in number to suit the number of cigarettes contained in a pack. The cigarettes drop down toward the bottom through the channels and emerge from the chute via three exits, each of which is designed to dispense a layer of cigarettes during the single work cycle of the packaging machine. The three layers are fed one by one into the pockets of an intermittent conveyor, where they form a group, normally of twenty cigarettes, arranged in a typical three-tiered honeycomb formation that represents the contents of one pack.
The entire body of cigarettes proceeding along the channels of the chute will normally be subjected to a quality control, generally to ascertain that the ends of each cigarette are properly filled with tobacco, or in the case of filter tips, to make sure that each of the cigarettes exhibits a filter. Such operations are usually effected by means of plunger pins located alongside each channel at a given point coinciding with the quality control station, and reciprocated axially through a path parallel with the axes of the cigarettes occupying the channels. Proceeding along the channels, the cigarettes will stop alongside the control station at a given point during each work cycle of the packaging machine, whereupon the plungers shift forward axially to the point of impinging upon their stationary ends.
In conventional devices, the position assumed by each plunger on accomplishing this axial shift may be detected in any one of a number of ways, and the result will be indicative of the conditions of the single cigarettes monitored. For example, the button of a switch may be associated with each plunger, in which case operation of the switch indicates that the end of the cigarette is correctly filled, or filter-tipped; failure of the switch to operate, on the other hand, will result in the activation of a reject signal which, in conjunction with a suitably programmed memory facility, causes the defective cigarette to be knocked out at a successive stage.
It has been discovered, however, that a quality control station of the type described above cannot guarantee the detection of every single defective cigarette, by dint of the fact that the switches utilized operate mechanically, and dependability is lost with the passage of time.
In other conventional devices utilizing plunger pins, each plunger is associated with a transducer, e.g. inductive or capacitive, positioned at right angles to the plunger and capable of sensing the position of a given part of the plunger, of greater or lesser diameter, on termination of its movement toward the cigarette.
This type of device, too, has been seen to be less than totally reliable, inasmuch as a certain degree of play will inevitably be established, again, with the passage of time, between the plungers and the holders in which they are slidably mounted, so that the plunger becomes subject to unwarranted radial movement. As the transducers, positioned normal to the pins, are highly sensitive, such radial movement can give rise to incorrect readings; for example, a small diameter part of the plunger may move radially into close proximity with the transducer as a result of the surrounding gap, the result of which is that such proximity is interpreted at a larger diameter by the transducer.
The object of the invention disclosed is to embody a quality control device, using plunger pins, that is free from the drawbacks described above, and will permit a sure verification of whether or not the cigarettes fed into the wrapping line of a packaging machine are properly filter tipped, and filled right to the end with tobacco.